By Default, when we login to CRM, we will have the below Sign in page. We can customize this, according to our Business requirements.

Follow the below steps for customizing the Company Branding of the CRM Sign in page in Dynamics 365 Online.
Prerequisite: Global Administrator access on Azure Portal.
Step 1: Create Dynamics 365 Online 30 days trial version or If you have an existing trial version, you can use it.
Note: For this example, i have created a CRM 30 day trial.
Step 2: Login to https://portal.azure.com/ with Global Administrator role.
Step 3: Click on View, under Manage Azure Active Directory.

Step 4: Click on Company Branding.

Step 5: Click on Configure.

Step 6: Provide all the necessary information.
Background image: Upload 1920 X 1080px image for the login page background.
Banner logo: Upload 280 X 60px image to show your company name.
Username hint: Text will be shown when users enters data in username input field
Sign-in page text: Text will be displayed at the bottom of the Login page.

Step 7: Once all the data provided, save the company branding.

Step 8: Now, try to browse your CRM or Azure Portal or Office 365, we can see our customized branding, on the Sign in page of your particular tenant.


Hope you have learned this feature and successfully customized the Sign in page for your customer.
Click here to know more info about Custom Branding.